Mixer-settler apparatus



y 1960 J. A. DUKES ET AL 2,937,078

MIXER-SETTLER APPARATUS Filed Jan. 25, 1957 m UE United States PatentMIXER-SETTLER APPARATUS John Alexander Dukes, Clifton, Preston, and FredParish,

Lea Preston, England, assignors to The United Kingdom Atomic EnergyAuthority, London, England Application January 25,1957, Serial No.636,406

Claims priority, application Great Britain February 3, 1956 1 Claim.(Cl. 23270.5)

This invention relates to mixer-settler apparatus for contacting twosubstantially immiscible liquids of differing densities.

The flow of fluids through a mixer-settler apparatus may be achieved byproviding for an overall gravityfall (i.e. vertical or inclinedapparatus) or by lifting during the course of mixing (e.g. air lift,centrifugal pump, a screw).

The mixer-settler apparatus of the present invention is horizontallyarrayed and possesses no positive lifting arrangements.

According to the present invention a mixer-settler apparatus comprises,in each mixer compartment, double impeller arrangement adapted to rotateabout a vertical axis, the impellers being arranged above and below aport between the mixer compartment and its associated settlercompartment and the double impeller arrangement being such that theupper impeller. drives downwards and the lower impeller drives upwards.

One form of mixer-settler apparatus embodying the invention will now bedescribed with reference to the accompanying drawing wherein Fig. l is afront elevation, with a cut away part, Fig. 2 is a front elevation of animpeller, and Fig. 3 is a side elevation of an impeller.

Fig. 1 shows the mixer-settler apparatus having a conrows indicate flowin the front row compartments, and

ventional layout, that is two adjacent rows of alternate I mixercompartments 10 and settler compartments 11. The compartments 10, 11alternate both along and across the rows, so that behind each front rowmixer compartment 10 there is an associated back row settler compartment11, and similarly in front of each back row mixer compartment 10 thereis an associated front row settler compartment 11.

In each mixer compartment 10 there is a simple double impellerarrangement comprising a vertical shaft 12 carrying an upper impeller 13and a lower impeller 14. At a level between the impellers 13, 14, atransfer port 15, interconnecting the mixer compartment 10, andassociated settler compartment 11, is shown. Referring to Figs. 2 and 3,the impellerhas a rectangular-section boss 16 drilled to provide a hole17 to fit on the shaft 12. (A grub screw 18 is available for locatingthe impeller on the shaft.) The boss 16 has two rectangular vanes 19, 20welded to it and inclined as shown in Fig. 3. The impeller 13 has vanesarranged in the opposite sense to those on impeller 14 so that, onrotation of the shaft 12 in the correct direction, impeller 13 forcesthe liquids in the mixer compartment downwards and the impeller 14forces the liquids upwards to produce mixing. I

The other features of construction are now described.

The mixer-settler is built in a container 21 and pro- The ports 23, 25,have outlet boxes 26, 27,

- 2,937,078 Patented May 17, 1960 respectively. Between mixercompartments 10 and ad jacent settler compartments 11 there areadjustable light phaseweirs 28' and heavy phase ports 29 with hoods 30.The shafts 12 are powered from an electric motor 31 driving throughachain 32a central shaft 33 running in journals 34, 35 supportedonst'ifieners 38. Four chain drives 36 are taken from the shaft 33 tobevel gears 37 which are coupled with the shafts 12 and supported onbrackets 39.

In alternative arrangements the impellers 13 and 14 are mounted onseparate shafts and: suitably driven.

In operation, the mixer-settler apparatus is used to extract metalvalues from an aqueous solution (the heavy phase) using an organicsolvent (the light phase) by repeatedly mixing and separating the twoliquids. The flow of the two liquids is as follows (dotted arrowsindicate flow in the back row compartments, full-line archain-dottedlines indicate levels).

The light phase flows in continuously from the port 22 (as shown byarrow 40) into the mixer compartment 10 at the right-hand end of thefront row. After mixing it flows through the port 15 to the associatedback row settler compartment 11, as shown by the tail symbol 41. Aftersettling, the light phase flows over a weir (like weir 28 in the secondfront row settler compartment 11) into the adjacent back row mixercompartment 10 and then, after mixing, through the port 15 into theassociated front row settler compartment 11, as shown by the pointsymbol 42. After settling, the light phase flows overv the weir 28, asshown by arrow 43, into the front row mixer compartment 10. This flowpattern is continued until the light phase enters .the settlercompartment '11 at the left-hand end of the front row, from which,

setller compartment 11, as shown by the point smbol 46. After settling,the heavy phase flows through the port 29 into the adjacent front rowmixer compartment 10, as shown by arrow 47. After mixing, the heavyphase flows through the port 15 into the associated back row settlercompartment 11, as shown by the tail symbol 48.

This flow pattern is continued until the heavy phase enters the settlercompartment 11 at the right-hand end of the back row, from which, aftersettling, it flows into the outlet box 27 and thence out through theport 25, as shown by arrow 49.

The general effect of the impellers in the mixer compartments can beregarded as driving the heavy phase entering the mixer compartmentsupwards (as shown by arrow 50) into the light phase and the light phaseentering the mixer compartmentsdownwards (as shown by arrow 51) into theheavy. phase thereby achieving intimate mixing. The head of mixed phaseabove the ports 15 coupled with the forces set up by the action of theimpellers is adequate to cause 'flow through the ports 15 against thehead of light phase above the ports 15 determined by the level of theweirs' 28, thus achieving flow in a horizontally arranged apparatuswithout using any positive lifting arrangements.

The speed of the shaft 12 is 300 rpm. and the throughput of the mixersettler is of the order of 3 cubic metres/hour with overall dimensionsof 70" long, 2'-3" high and 5'-3f' wide.

We claim:

A mixer-settler apparatus for. contacting two substantially immiscibleliquids of differing densities comprising e 3 a first row of alternatesimilar mixer compartments and similar settler compartments, a secondrow of alternate similar settler compartments and similar mixercompartments, each mixer compartment in one row being associated with asettler compartment in the other row by means defining a transfer portfor flow from mixer to settler compartment, the mixer compartments atthe ends of the apparatus each having means defining an inlet port, thesettler compartments at the ends of the apparatus each having meansdefining an outlet port, each settler compartment having an overflowweir connecting with the mixer compartment on one side of said settlercompartment and means defining an underfiow port con meeting with themixer compartment on the other side of said settler compartment, and ineach mixer compartment two impellers adapted to rotate about a commonvertical shaft, the upper impeller being disposed above said transferport and adapted to drive downwards and the lower impeller beingdisposedbelow said transfer port and adapted to drive upwards.

References Cited in the file of this patent UNITED STATES PATENTS1,297,170 Holley et a1 Mar. 11, 1919 1,297,171 Holley et a1. Mar. 11,1919 2,139,871 Wilson et a1. Dec. 13, 1938 2,614,821 Tatman Oct. 21,1952 2,709,680 Watson May 31, 1955

